1. Field of the Invention
The invention relates to a microtome for the production of histological sections, particularly of plant and animal tissues, which are intended for microscopic inspection.
2. Discussion of Prior Art
So-called slide microtomes are known from the Soviet Inventor's Certificate SU-783626 or from the Applicant's EP-A1 0 416 354, and have a baseplate with an object carrier and in addition substantially horizontal guides. A knife holder is movably received in the horizontal guides and is provided with a handle. The knife holder moves back and forth, linearly and horizontally, and its motion is coupled with a feed drive of the sample carrier.
Slide microtomes are distinguished by their simple construction and the consequent low price. Moreover they are distinguished, as long as the user follows a sufficient routine, by operation which is not tedious. On the other hand, it is a disadvantage that the removal of the microtome sections is quite complicated. This disadvantage clearly becomes manifest in the latest slide microtomes, which have an electrical drive of the sample feed, such as that offered by the Applicant under the designation "OHM 440". Indeed, because of the electrical sample feed, the knife holder no longer needs to be moved over the whole length of the guideway in order to cause the sample feed. Instead, it is sufficient to move the knife or the knife holder over a path length which roughly corresponds to the thickness of the sample along the direction of cutting, since the electronics of the sample feed detects the reversal of motion of the knife holder. Thus with small samples, a substantially higher cutting frequency is possible. However, it has been found that the time required for removal of sections limits the cutting frequency.
Moreover, so-called rotary microtomes are known, which are described, for example, in DE-P 33 01 921 or in DE-C1 35 39 138. Such a rotary microtome usually has a baseplate on which a slide with a cutting knife, movable parallel to the baseplate, is received. The slide with the sample carrier is received in a further guide, which is directed substantially perpendicular to the baseplate and consequently permits a motion of the sample carrier perpendicular to the baseplate. The drive of the cutting motion, which runs perpendicular to the baseplate, of the sample carrier takes place by means of a hand crank in the form of a disc with a horizontal axis of rotation.
As regards removal of sections, such rotary microtomes are considerably more user-friendly than slide microtomes, since the sections which are produced are produced in the forward region of the microtome, lie on the back face, inclined forward and downward, of the microtome knife or knife holder, and can be floated off there, for example by the use of a water bath. However, such rotary microtomes have the disadvantage that the rotary motion of the handle is quite tiring. The number of sections produced during the course of a working day is thus lower for rotary microtomes than for slide microtomes.
It would be conceivable to provide a motor to drive the cutting motion, in order to eliminate this disadvantage. However, the motors which would be required for this would nearly double the price of the microtome.